Apparatus for refining metals



. 1,628 375 May 10,1927. l M. UNGER APPARATUS FOR REFINING METALS FiledDec. 31, 1925 l-fs- 3o Fig. 2.

Inventor- Ilflc'gnus Unger,

HLS Attorny,

vPatented May 10, 1927.'

UNITED JSTATES lPATENT OFFICE. Y

IAGNUS UITGEB, OF PITTSFIELD, MASSACHUSETTS, .ASBIGNOR T0`r GENERALELFE- TBIC COMPANY, A COBIORATIONYOF NEW YORK.

Arranarus ron narrante Marlins.y

plantation and December s1, 1925. sum1 No. vaas?.

or control of the silicon content so that the product may be of uni-formquality as well as having the desired silicon content. vIn order to dothis with certainty it is necessary to hold the steel in a moltencondition for a suiiicient interval of time to enable lthe steel to beanalyzedv to determine the amount of silicon and the amount of siliconregulated. if necessary. Furthermore, molten steel as received from theopen hearth vfurnace or the Bessemer converter has been found to containa considerable amount of gas which it has absorbed. The volume. of thisabsorbed gas at atmospheric pressure may be many times-the volume of thesteel by which it isk absorbed. It is a further object of my inventionto provide means` whereby the steel may be maintained molten foraconsiderable interval to permit 'this gas toescape.

In carrying out my invention in one form I reduce. the molten steel intoa ladlev in which it remains for a considerable interval to rovide forthe escape of as and for ana ysis. Associated with the adle I haveprovided inductive means whereby the steel may be heated to maintain itstemperature or give it any desired superheat, the inductive means beingalso so arranged as to pro' duce a circulation, and thereby' thoroughmixing, of the molten metal by electromagnetic repulsion.

For a more complete understanding of my invention reference should behad to the accompanying drawing in which Fig. 1 is a. vertlcal sectionalview of apparatus for refining silicon steel embodying m invention; Fig.2 is a sectional view a ong the,

line 2 2 of Fig. 1 looking in the direction of the arrows; Fig. 3 is asectional view along the line- 3f-3 of Fig. 1 looking in the directionof the arrows; while Figs.' 4 and 5 are views showing details ofconstruction. Referring to the drawing, in one embodi- ,which the ot'the greatest difficulties incident to the'makmg of silicon steel is theregulation i Y reservoir.

my invention I providea ladle in i molten steel 1s introduced andmamtamed for a considerable interval for rehnmg. 'This ladle comprisesan inner heat insulated provide a ment of reservoir 11 for the metal andan annular channel 12 in which a portion of theA molten metal lforms aclosed secondary for crucible l0 which is 'shaped toa primary winding 13associated therewith.

The annular channel is arranged in a hori zental position, 1. e., withits axis substan-K tially vertical at one side of the reservoir l1 aslight distance above the bottom of the lt is connected with thereservoir .through three ducts provided in the refractory material ofthe crucible, two of these ducts 14 and 15 connecting the upper axialend of the channel and the third duct 16 connecting the lower axial endof' the channel with the reservoir. The two .ducts 14 vand 15 are eachsubstantially one half the cross sectional area' of the duct 16 and arespaced apart laterally, i. e., in a direction-v at right angles to theaxis of the channel, so as to communicate at opposite sides of the upperend of the channel. The lower duct 16 is situated laterallysubstantially midway between the two upper ducts, it being'spacedaxially with respect to the other two duct-s as previously noted.

The crucible 10 is made from aA suitable refractory material lsuch as amixture of fused magnesia, calcined magnesia,' and a with the reservoirbinder. such as magnesium sulphate, as described and claimed in Patent No. 1,444,527 to Scharschu dated February 6,1925. These materials aremixed in granulated or powdered form,l suiicient water being added to'make a plastic mixture and the mass thus'.

formed is rammed` in place around a suitable core which .defines thereservoir, the

.channeland the ducts.v Preferably a hollow receptacle-like member 21 isprovided as aY core for gie reservoir and the annular core is connec dto it by means of steel tubes los 22, 23 and 24 which define the ducts.ends of the tubes are butted or welded to the outer tube 18 and thereceptacle 2l, and

communicate with the interiors thereof as indicated in Fig. 4.Surrounding the crucible 1() is a layer of suitable refractory heatinsulating material 25, the whole being enclosed by an outer metalliccasing 2G. ln constructing the ladle the insulating material 25 is builtup inside the casing 26, suieient space being left for the crucible 10.rllhe bottom-layer of the crucible is then rammed in place after whichthe steel core for the channel, ducts and reservoir is placed on thisbottom layer and the ramming in of the crucible continued until thedesired thickness of material has been formed around the core. The heatinsulating material around the upper portions of the crucible is thenfilled in and the remaining upper portions of the casing secured inplace.

An aperture for the primary winding 1? is provided by means of a heatrefractory cylinder 27, made of high grade fire clay, preferably havinga high alumina conte at. This refractory cylinder 27 effectivelyprotects the primary winding from contact with the molten metal in caseof a'leak through the rammed crucible 10. A further protection isprovided by a metallic tube 28 inserted inside the refractory tube 27,this tube 28 being split longitudinally at 29 to prevent its acting as aclosed secondary for the primary winding. As shown, the primary windingis mounted on a` three legged core 30, the middle-leg on which theprimary winding is secured passing through the metallic tube 28.

The ladle is mounted on suitable rockers 31 and 32 which rest on tracks33 and 34,.

and it may be tilted by means of a suitable hydraulic motor 35 in orderto pour the metal from the spout 86.

After the crucible 10 is rammed it is allowed toI dry, this operationbeing completed by the application of heat. The drying or burningoperation is carried out by means of suitable blow torches which areapplied to the inner wall of the hollow core member, the flame of thetorch being carried around through the hollow portions of the coremember forming. the ducts 14, 15 and 16, and the annular channel 12. Theannular portion'of the core member may be furit from the primarywinding. During this drying or burning operation the hollow core memberserves to protect the inner surface of the rammed material from injuryby reason of direct contact with the flame of the blow torch and alsoserves to support the material. The material has a stage of greatweakness during the drying or burning operation so that it might crumbleif it were The"- unsupported. The hollow core member thus makes itpossible to apply heat to dry the rammed material and at the same timeit acts as a support for the material.

After the crucible has been dried, the ladle may be put in operation bypouring in a charge of molten steel which ills the hollow core memberdeiining the channel and the ducts. The primary winding is thenenergized whereby heating currents are induced in the section of thecore forming the channel and in the molten metal contained therein. Thecore member is thus melted and mixed with the charge.

ln utilizing the ladle the molten steel may be introduced either from anopen hearth furnace or Bessemer converter, er an electric furnace, arelatively small quantity being introduced at each time. F or example,with a 24 ton ladle the ladle will be initially filled and 8 tons pouredat the end of the reining operation leaving 16 tons, and thereafter 8tons will be added to the ladle. The steel is left. in Athis ladle for aconsiderable interval, for example, three or four hours during `whichtime the absorbed gases are caused to escape and the composition of themetal can be dcterminedand regulated as desired. .y

During this period the metal will`be maintained molten or superheated toa desired temperature by means of heat generated by the induced currentsin the portion of the metal in the annular channel, these currents beinginduced by the primary winding.

Furthermore, the primary winding 1s so associated with the molten metalin the channel that a circulation is produced by electromagneticrepulsion. For` example, the primary winding may be displaced axiallydownward so as to exert an upward repulsive force. In` other words, theprimary winding as shown in the drawing has its lower end projectingbelow the secondary channel so that its axial center isbelow the axialcenter of the secondary. This disposition of the primary winding resultsin upwardly directing the repulsive forces acting on the moltenv metalin the channel, these forces being cumulative in an upward direction sovthat the metal in the upper axial end of the secondary channel is undera greater pressure than that at the lower end. This causes the metal toflow out of the secondary channel into the reservoir through the upperducts 14 and 15, a return-flow of molten metal from the reservoir to thechannel through the duct 16 being thereby produced. The circulation ofthe molten metal thoroughly mixes it as well as distributing heatgeneratedin the channel. The mixingeffect produced by the inductiveheating apparatus is of great importance since the molten metal ismaintained of uniform quality and any additional metal suchv as siliconadded to raise Ithe silicon content, i's thoroughly mixed With the metalalready in the crucible. V

In order to provide for the rapid escape of the gases from the moltenmetal, the metal isv preferably allowedto cool almost to the point ofsolidification after which its temperature is raised quickly forpouring.

While I have described my invention as embodied in concrete form and asoperating in a specific manner in accordance with the provisions of thepatent statutes, it should be understood that I do not limit myinvention thereto, since K various modifications thereof will suggestthemselves to those skilled in the art Without departing from the spiritof my invention, the scope of which is set forth in the annexed claims.

What I. claimv as new and desire to secure by Letters Patent of theUnited States, is:

vl. A Crucible for molten metal comprising refractory material forming areservoir for the charge and an annular channel in which a portion ofthe Charge forms a closed secondary, said refractory material providrmgtwo openings spaced 1n a directlon at i right angles to the axis of saidchannel connecting one end of said channel with said reservoir, and asingle opening connecting .Y

the opposite endpof said channel With said reservoir, and a primarywinding arranged to induce heating currents in said secondary andproduce circulation of molten charge by electromagnetic repulsion.

2. A mixing and` refining Crucible for molten metal comprisingrefractory material forming a reservoir for the charge and lateralextremities of said channel and res-` ervoir and a single openingconnectlng the lower end of said channel with said reservoir at a pointlaterally intermediate said upper openings, and a primary windingarranged to induce heating currents in said secondary and producecirculation of molten charge between said channel andreservoir byelectromagnetic repulsion.

3. Electric induction heating apparatus comprising heat refractorymaterial formf ing a reservoir for a charge and an annular channelhaving its axis arranged substantially vertical in which a portion ofthe charge forms a closed secondary, said refractory material providingspaced openings connecting the upper end of said channel With saidreservoir and a single opening connecting the lower end of said channelwith said reservoir, and a primary winding inserted in said secondary,said primary winding being axially displaced in a downward directionwith respect to said channel whereby a magnetic repulsive force isexerted on said secondary in an upward direction to produce acirculation of molten charge between said secondary and said reservoir.

In witnem whereof, I have hereunto set my hand this 28th day ofDecember, 1925.

MAGNUS UNGER.

